In order to test the safety and efficacy of SmithKline Beecham Biologicals' herpes simplex vaccine (gD-Alum-MPL), a double-blind, randomized, placebo controlled study will be conducted in healthy adult volunteers with or without positive serological markers of herpes simplex infection (HSV1 and/or 2) but without genital herpes disease. The vaccinations will be given at 0, 1 and 6 months. Safety and humoral immune response follow-up visits will extend until Month 19. Since herpes simplex infections are extremely common, determination of the safety and efficacy of an HSV vaccine has immense prophylactic and therapeutic indications.